The invention relates to a spinning machine having several spinning points, at least one drafting unit being assigned to each of these spinning points and each drafting unit containing several top rollers and several drivable bottom rollers. At least the bottom rollers which are assigned to the feeding side for the fiber material are driven by a common drive shaft extending in longitudinal direction of the machine by means of transmission devices which contain a shiftable coupling.
Spinning machines having drafting units of the initially mentioned type are known (JP-A 59-15519, JP-A 62-69832, JP-A 62-162029). In these constructions, the bottom rollers of the respective drafting units are mounted in a common transmission case from which the bottom rollers project away, in an overmounted manner, toward one side or toward two opposite sides. The bottom rollers are driven by drive shafts which extend through in the longitudinal direction of the machine and are connected to the bottom rollers by means of wheel gears. A shifting coupling is also provided in these wheel gears. In the case of spinning machines of this type, it is possible to stop the drafting units of an individual spinning point; i.e., to switch off the drafting unit without, as a result, interfering with the drafting unit of the adjacent spinning points.
An object of the invention is to develop a spinning machine of the initially mentioned type in such a manner that a further improvement is obtained.
This object is achieved according to preferred embodiments of the invention in that at least the bottom rollers assigned to the feeding side are arranged adjustably for the purpose of adjusting the distance with respect to the respective following rollers.
By means of this construction, it is possible to adapt the drafting zone widths to the fiber material to be processed and thus optimize the drafting operation.
In a further development of the invention, it is provided that the transmission devices arranged between the drive shaft and the bottom rollers form a step-down gear. As a result, the circumstance is taken into account that, according to practical experiences, a drive shaft, which passes through in longitudinal direction of the machine, has better concentricity characteristics if it does not fall below a certain rotational speed. As a result, it becomes possible to provide the drive shaft with a sufficiently high rotational speed, and to nevertheless provide relatively low speeds for the bottom rollers, particularly on the feeding side.
In a further development of the invention, a shifting device is provided which actuates all couplings of the bottom rollers of a drafting unit together. As a result, it becomes possible to simultaneously stop all bottom rollers of a drafting unit, if they are driven individually, so that no additional breakage of the sliver or of the roving takes place within the drafting unit. This results in fewer problems for the start of a piecing in which fiber material must be fed again.
In a further development of the invention, toothed wheels are provided as transmission devices which are advantageously made of a plastic material. Toothed wheels of this type permit a precise maintaining of the rotational speed and thus a precise maintaining of the adjusted draft. However, they require no lubrication so that there is relatively little danger that the fiber material may become dirty.
In a further development of the invention, it is provided that an intermediate wheel is arranged between a toothed wheel of the drive shaft and a toothed wheel of the bottom roller. As a result, it becomes possible to implement a higher gearingdown. In a further development of this construction, it may be provided in this case that the intermediate wheel, by means of an adjusting device, can be disengaged from the toothed wheel of the bottom roller and/or from the toothed wheel of the drive shaft. This intermediate toothed wheel and the pertaining adjusting device may be utilized to function as a coupling by means of which the drive of the respective bottom roller may be connected or disconnected. A separate shiftable coupling will then not be necessary.
In a further development of the invention, it is provided that one toothed belt drive respectively is provided as the transmission device between the drive shaft and the bottom rollers. Synchronous belt drives of this type also permit a precise maintaining of rotational speeds without any limitations with respect to space. In a further development of this embodiment, it is provided that the toothed belt drive is equipped with devices for disengaging a toothed belt from a toothed wheel connected with the drive shaft or the bottom roller. As a result, it is also possible to interrupt the drive and switch it back on by the disengaging and engaging of the toothed belt so that a separate shifting coupling is not required.
In a further development of the invention, it is provided that, as the transmission devices for the same drafting unit, toothed wheels are provided between one or several bottom rollers and one or several drive shafts extending in longitudinal direction of the machine, and toothed belt drives are provided between one or several bottom rollers and a drive shaft. As a result, the circumstance is taken into account that the toothed wheels may possibly cause difficulties at high speeds. This type of a toothed belt drive may then be provided particularly for the bottom rollers on the delivery side.
In some applications, it may be sufficient, in the case of a yarn breakage, to stop only the bottom rollers of the feeding side and perhaps also the bottom roller or the two bottom rollers which are next in moving direction of the sliver. It will then be possible to provide, particularly for the bottom rollers of the delivery side, no possibility for an individual stopping. In this case, these bottom rollers of the delivery side may then be constructed as shaft which extend through in the longitudinal direction of the machine, as customary today in drafting units for all bottom rollers.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.